1. Field of the Invention
This invention relates to an actuator with an electric motor as its drive source, namely, a motor-operated actuator which is employed, for instance, for locking a door of an automobile.
2. Description of the Prior Art
A motor-operated actuator of this type has been disclosed by. Examined Japanese Patent Publication Sho-58-47551/(1983) and Unexamined Japanese Patent Publications Sho-60-113856/(1985) and Sho-60-253680/(1985). In order to lock and unlock the door not only by remote operation but also by manual operation, the motor-operated actuator generally includes a clutch mechanism which disengages a door lock mechanism from the motor except when the actuator is actuating to lock or unlock the door by remote operation.
FIG. 6 is a front view showing the installation of the above-described door lock actuator. FIG. 7 is a plan view showing the internal structure of the actuator. FIG. 8 is a sectional view taken along line 8--8 in FIG. 7. FIG. 9 is a diagram showing a link bar in detail. FIG. 10 is an exploded perspective view of a clutch mechanism. As shown in the figures, the door lock actuator 1 is coupled to a clutch mechanism 2 through a rod 3. More specifically, the actuator 1 has an output shaft 4, to which a link bar 5 is fixedly secured. The free end of the link bar 5 is coupled to one end of the rod 3 by a clamp 6, the other end of which is coupled to a pin located at the middle portion of a lever 2a, which has a lock knob 2b at the end. The actuator 1 comprises a housing made up of an actuator body 7 of synthetic resin and a cover 8 coupled to the actuator body 7 with screw. The actuator body 7 has mounting pieces 9 at both ends. Each of the mounting pieces has a through-hole 9a with a cut With the mounting pieces 9, the actuator 9 is secured inside the door with screws. The output shaft 4 coupled to the above-described door lock mechanism 2 is engaged through a seal 12 with a hole 10 formed in the actuator body 7, in such a manner that it protrudes outside the actuator body 7.
An electric motor 13 is arranged in the actuator body 7. The motor 13 has an output shaft 13a, on which a small gear 14 is mounted as a speed reduction mechanism. The small gear 14 is engaged with a gear 15, which is coupled to a pinion gear 17 through a spring 16 which is elastic in the direction of rotation. The pinion gear 17 is engaged with external teeth 21d of a clutch input gear 21. The clutch input gear 21, as shown in FIGS. 11A to 11C, has roller guide walls 21a and 21a like the slopes of a sector, and an arcuate lever hole 21b. The roller guide walls 21a and 21a, as shown in FIG. 11A, are engaged with rollers 22 and 22 coupled to both ends of a return spring 23. Reference numeral 19 designates a lever drum on which a brake spring 20 is elastically mounted. The brake spring 20 has both end portions 20a which are abutted against a stopper 7a of the actuator body 7, so that it is fixedly positioned. A lever 19a is protruded from one side of the lever drum 19, and is inserted into the lever hole 21b of the clutch input gear 21. Reference numeral 24 designates a clutch output gear. The clutch output gear 24 has transmission protrusions 24a, which are engaged with an inner wall 21c of the clutch input gear 21 so that the latter 21 is combined with the clutch output gear 24. The clutch input gear 21, the lever drum 19, and the clutch output gear 24 are rotatably mounted on one and the same clutch shaft 25. The clutch output gear 24 has a gear 24d, which is engaged with an output gear 26. The output gear 26 has a protrusion 26a, which is elastically engaged with a plate 27 which is fixedly secured to the above-described output shaft 4 by caulking.
Now, the operation of the actuator thus constructed will be described. When the lock mechanism 2 is in unlock state with the lock knob 2b pulled up, the link bar 5 of the door look actuator 1 is on the UNLOCK side. When, under this condition, the operator sets a predetermined switch (not shown) to "LOCK", a hold circuit (not shown) is activated so that the motor 13 is rotated for a predetermined period of time (for instance 0.5 second), so that the rotation of the motor is transmitted through the small gear 14 and the reduction gear 15 to the pinion gear 17 to rotate the latter 17 while rotating and compressing the spring 16.
The rotation of the pinion gear 17 is transmitted to the clutch input gear 21 so that the clutch is connected. This will be described in more detail. As shown in FIG. 11A, the clutch input gear 21 is turned clockwise relative to the lever 19a. In this operation, the movement of the roller 22 is prevented by the lever 19a, while the return spring 23 is stretched. As a result, the roller 22 is moved radially outwardly along the roller guide wall 21a until it abuts against the clutch input gear's inner wall 21c (FIG. 11B). In this operation, the brake spring 20 allows to slide on the lever drum 19, and therefore the lever 19a is turned at the same speed as the clutch input 21.
As the clutch input gear 21 is turned, the roller 22 moved radially outwardly is engaged with the transmission protrusion 24a of the clutch output gear 24, to turn the latter 24. As the clutch output gear 24 is turned in this manner, the output shaft 4 is turned through the output gear 26 and the plate 27, so that the lever 2a is pulled down through the link bar 5 and the rod 3. As a result, the look mechanism 2 is operated as indicated by the phantom line; that is, it is placed in a lock state. When a predetermined period of time elapsed, the supply of current is suspended by a timer, so that the repulsive force of the spring 16 causes the motor 13 to turn in the reverse direction. As a result of the reverse turn of the motor, the clutch input gear 21 and the clutch output gear 24 are loosened from each other as indicated by the dotted line in FIG. 11C. Therefore, the roller 22 is returned to the initial position (FIG. 11A) by the elastic force of the return spring 23, so that the clutch is disconnected. The above description can be equally applied to an operation that the locked door is automatically unlocked, and an operation that the unlocked door is manually locked.
The conventional motor-operated actuator is constructed as described above. Therefore, as the return spring 23 is deteriorated, or the gears are increased in the resistance of rotation because of low temperature, the rotation of the motor in the reverse direction upon completion of the operation of the actuator is decreased, with the result that the roller 22 may not be returned to the initial position in the clutch. If, under this condition, the next operation (in the opposite direction) is carried out, then the roller 22 may be moved from its predetermined operating position being pushed by the transmission protrusion 24a of the clutch output gear 24. As a result, the roller 22 may be disconnected from the return spring 23; that is, the clutch mechanism may be broken. In addition, it is rather troublesome to connect the rollers 22 to the returned spring 23.